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HTML5 canvas做的一個圖片局部放大的效果

日期：2017/3/1 10:37:07 编辑：Linux編程

看到老外做HTML5的越來越多了,今天看到一個其中用HTML5做的效果不錯, 是在canvas上畫的圈,做放大器,並且監視了鼠標的相關事件,代碼如下:

HTML部分

<!DOCTYPE html>
<html lang="en" >
<head>
<meta charset="utf-8" />
<title>HTML5 canvas - Image zoomer | muu.cc</title>
<link href="css/main.css" rel="stylesheet" type="text/css" />
<script type="text/javascript" src="js/jquery-1.5.2.min.js"></script>
<script type="text/javascript" src="js/script.js"></script>
</head>
<body>
<div class="container">
<canvas id="panel" width="800" height="533"></canvas>
</div>
<footer>
<h2>HTML5 canvas - Image zoomer</h2>
<a href="http://www.muu.cc" class="stuts">Back to original MUU.cc on <span>MUU CC</span></a>
</footer>
</body>
</html>

CSS部分:

*{
margin:0;
padding:0;
}
body {
background-color:#bababa;
color:#fff;
font:14px/1.3 Arial,sans-serif;
}
footer {
background-color:#212121;
bottom:0;
box-shadow: 0 -1px 2px #111111;
display:block;
height:70px;
left:0;
position:fixed;
width:100%;
z-index:100;
}
footer h2{
font-size:22px;
font-weight:normal;
left:50%;
margin-left:-400px;
padding:22px 0;
position:absolute;
width:540px;
}
footer a.stuts,a.stuts:visited{
border:none;
text-decoration:none;
color:#fcfcfc;
font-size:14px;
left:50%;
line-height:31px;
margin:23px 0 0 110px;
position:absolute;
top:0;
}
footer .stuts span {
font-size:22px;
font-weight:bold;
margin-left:5px;
}
.container {
color:#000;
margin:20px auto;
position:relative;
width:800px;
}
#panel {
border:1px #000 solid;
box-shadow:4px 6px 6px #444444;
cursor:crosshair;
}

script.js

// variables
var canvas, ctx;
var image;
var iMouseX, iMouseY = 1;
var bMouseDown = false;
var iZoomRadius = 100;
var iZoomPower = 2;
// drawing functions
function clear() { // clear canvas function
ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
}
function drawScene() { // main drawScene function
clear(); // clear canvas
if (bMouseDown) { // drawing zoom area
ctx.drawImage(image, 0 - iMouseX * (iZoomPower - 1), 0 - iMouseY * (iZoomPower - 1), ctx.canvas.width * iZoomPower, ctx.canvas.height * iZoomPower);
ctx.globalCompositeOperation = 'destination-atop';
var oGrd = ctx.createRadialGradient(iMouseX, iMouseY, 0, iMouseX, iMouseY, iZoomRadius);
oGrd.addColorStop(0.8, "rgba(0, 0, 0, 1.0)");
oGrd.addColorStop(1.0, "rgba(0, 0, 0, 0.1)");
ctx.fillStyle = oGrd;
ctx.beginPath();
ctx.arc(iMouseX, iMouseY, iZoomRadius, 0, Math.PI*2, true);
ctx.closePath();
ctx.fill();
}
// draw source image
ctx.drawImage(image, 0, 0, ctx.canvas.width, ctx.canvas.height);
}
$(function(){
// loading source image
image = new Image();
image.onload = function () {
}
image.src = 'images/image.jpg';
// creating canvas object
canvas = document.getElementById('panel');
ctx = canvas.getContext('2d');
$('#panel').mousemove(function(e) { // mouse move handler
var canvasOffset = $(canvas).offset();
iMouseX = Math.floor(e.pageX - canvasOffset.left);
iMouseY = Math.floor(e.pageY - canvasOffset.top);
});
$('#panel').mousedown(function(e) { // binding mousedown event
bMouseDown = true;
});
$('#panel').mouseup(function(e) { // binding mouseup event
bMouseDown = false;
});
setInterval(drawScene, 30); // loop drawScene
});